Journal of Natural Pesticide Research最新文献

Background

Theobroma cacao (Cocoa) is a major foreign exchange earner for Ghana. Over the recent decades, there has been a consistent decline in cocoa production in the country. A major contributing factor is the cocoa black pod disease caused by Phytophthora species. Synthetic fungicides have been used to control the pathogens over the years. However, recent calls for organic cocoa devoid of residues from synthetic fungicides, which are known to pose several health challenges as well as a negative impact on the environment, have gained attention. Thus, inviting investigations into more environmentally friendly and sustainable alternatives to synthetic fungicides.

Objective

This study explored the inhibitory potential of crude extract from Carica papaya against cocoa black pod disease caused by Phytophthora spp.

Material and methods

An in-silico study was done using known phytochemicals from Carica papaya as ligands against a Phytophthora effector protein. Crude extracts were obtained from the plant materials using 70 % ethanol as the extraction solvent. The crude Green Leaf Extract (GLE), Aging Induced Chlorophyll Deficient Leaf Extract (AICDLE), and Matured Black Seed Extract (SDE) were tested in-vitro against pre-cultured P. palmivora and P. megakarya using the poison food technique. GLE was modulated with Delco, a synthetic fungicide, at different ratios which were tested in-vitro and in-vivo.

Results

A total of 16 ligands showed binding affinity higher or equal to the standard ligand, alliin, suggesting Carica papaya as a repository of anti-phytophthora agents. Assessment of crude extracts at concentrations 5–20 mg/ml showed fungistatic activity against P. palmivora and P. megakarya in-vitro. Modulation of GLE with Delco produced some combinations that made GLE fungicidal in-vitro against P. palmivora and P. megakarya with fractional inhibition concentration indices between 0.51 and 0.65, interpreted as partially synergistic. The in-vivo assessment of combination D (Delco and GLE in a 0.3 mg:3 mg per ml ratio) performed as well as Delco alone at the recommended dose of 5 mg/ml. Thus, combination D reduces the requirement for copper-based fungicide by over 90 %.

Conclusion

This study shows Carica papaya in a new light as a potential material that could be formulated into a natural product-based fungicide for combating Phytophthora-induced black pod disease.

Sustainable agricultural systems demand less or no use of synthetic chemicals, which have various adverse effects on the environment and human health. In this context, studies on phytochemicals with antimicrobial and antioxidant properties hold great promise to suppress plant diseases and, thereby, reducing the application of synthetic chemical pesticides. Such an alternative approach requires screening and identification of bioactive compounds from various plant species. In the present study, Guizotia abyssinica L., an oilseed crop plant that usually requires less water with no pesticide inputs to grow, was screened for its potential antioxidant and antimicrobial phytochemicals. The methanolic and aqueous extracts of leaves and flowers of G. abyssinica were tested for their polyphenol content (total phenols and flavonoids) and antioxidant potential. The antioxidant and free radical scavenging activities of both methanolic and aqueous extracts were higher in comparison to many previously reported plant extracts. Furthermore, leaf extracts of G. abyssinica have shown slightly higher antioxidant activity than flower extracts. In vitro antimicrobial studies confirmed the inhibitory effect of methanolic extracts of leaves and flowers against phytopathogens like Xanthomonas oryzae RR24, Fusarium sp. and Alternaria sp. The chemical nature and composition of these crude extracts were analyzed by Fourier Transform Infrared Spectroscopy (FTIR) and Gas Chromatography Mass Spectrometry (GC-MS). Approximately, 28 bioactive compounds detected in GC-MS were predicted to have antimicrobial activity. Based on our results, we conclude that the extracts derived from G. abyssinica have demonstrated remarkable efficacy in inhibiting the proliferation of phytopathogens, thus exhibiting immense potential in promoting sustainable agricultural practices.

The objective of this study was to examine the chemical composition of essential oil A. indica leaves and its nanoemulsion, and evaluation of potential for use as a biopesticide. Essential oil of A. indica extracted from fresh leaves was found to be 99.97% composed of 59 components, according to GC-MS analysis. A non-ionic surfactant Tween 80 and the essential oil of A. indica were combined to create a stable nanoemulsion using sonication method. A long durable stable nanoemulsion was obtained after thirty minutes of sonication, and it was examined using TEM (Transmission electron microscopy), DLS (Dynamic light scattering), and FTIR (Fourier transform infrared spectroscopy) analyses. To consider its practical applications, other factors such as stability, viscosity, pH, turbidity, and creaming index were also investigated. Antibacterial properties of essential oil and nanoemulsion were evaluated against bacterial blight plant pathogens Xanthomonas oryzae and Xanthomonas citri. The MIC (Minimum inhibitory concentration) was determined using the broth microdilution method, and the anti-Xanthomonas activity was assessed utilizing by agar disc diffusion method. Using the crystal violet (CV) technique, inhibition of biofilm formation and development were evaluated. Disturbance of bacterial membrane permeability was confirmed by estimating the proteins and nucleic acids (DNA, and RNA) leakage from the cell membrane. Greenhouse studies using rice/paddy plants were conducted to demonstrate the antibacterial potential of essential oil and nanoemulsion, using RNR-15048 rice cultivar by seed treatment and foliar spray groups. Results of the investigations suggest that, when the essential oil was transformed into a nanoemulsion, its antibacterial effect against bacteria was significantly increased, that might be attributed to the essential oil enhanced ability to penetrate the bacterial cells. Essential oil of A. indica and its nanoemulsion reduced rice bacterial blight disease by 84%and pathogen-virulence by 92%, and promoted the growth and development of rice/paddy seedlings. These results confirm that A. indica essential oil and its nanoemulsion possess anti-bacterial blight properties, without affecting growth and development of host plants. Essential oil of A. indica and its nanoemulsion could be used as biopesticide to control Xanthomonas induced bacterial blight diseases in crop plants either by using for seed treatment or as a foliar spray.

Kalmegh [Andrographis paniculata (Burm. F.) Wall ex. Nees] is one of the significant medicinal plants which possess active ingredients of therapeutic potential, widely used in the treatment of anti-inflammatory, anti-bacterial, anti-oxidant, hepatoprotective, etc. The plant is widely used in the Ayurvedic and homeopathic systems of medicine. In spite of this, kalmegh exhibits insecticidal and repellent properties against pests and insects of important medicinal significance and can be used as a promising bio-insecticide/pesticide. All the useful collective information and the database of the review are generated from the previously published articles using Web of Sciences, PubMed, Google Scholar, and other web searches. It possesses biopesticidal/insecticidal properties such as suppressing feeding activity, anti-oviposition activity, and weedicide of Plutella xylostella, Spilaractia obliqua, Callosobruchus chinesis L., Nephotettix cincticeps, Helicoverpa armigera, Parthenium hysterophorus, etc. Thus this review will provide some positive aspects towards the research for exploration and further studies in the future. This review outlines the summary of factual records of previous research concerning its ethnobotany, phytoconstituents, and bio-insecticidal/pesticidal potential of the crop. However, in the research sector, Andrographis paniculata's prospects will be on an upswing, the demand of the crop burgeoning in the industries, and eventually, farmers also reaping its benefits.

Brazil is affected by the infection of gastrointestinal nematodes (Haemonchus spp.) because it causes subclinical diseases in small ruminants that directly affect weight and milk production and, in turn, generate a health risk for the animals. In the same way root-knot nematodes (Meloidogyne incognita) is a serious disease, which parasitize the roots of tomato plants causing damage such as poor nutrient absorption leading to significant yield losses. In order to minimize the economic impact of these nematodes, it is important to establish new control strategies. Beauveria bassiana and Metarhizium anisopliae are two main mycoinsecticides used to control many orders of insects, such as Lepidoptera and Hemiptera. These fungi have the ability to produce extracellular enzymes, which play an important role to control in the pest infection process. The aim of this study was to evaluate the production of proteases and chitinases by the entomopathogenic fungi B. bassiana and M. anisopliae on different solid and liquid culture media and their application in vitro to the control of Haemonchus spp and Meloidogyne incognita. To achieve this goal, enzymes were produced under solid and liquid fermentation conditions to determine the highest chitinolytic and proteolytic activity of commercial two strain of B. bassiana (IBCB 66 and ESALQ PL63) and M. anisopliae (IBCB 425 and ESALQ E9) in liquid media: SDY broth, YPG culture medium, synthetic, and soluble starch with yeast extract. The solid media tested were: rice supplemented with whey and chrysalis flour mixed with rice. In addition, the nematicidal action of their extracts (containing concentrated enzymes and without fungal cells) was measured. The results showed that the best culture medium (p< 0.01) for protease was solid serum rice medium, with a value for M. anisopliae IBCB 425 of 52 U/mg, and for B. bassiana ESALQ PL63 the value was 36 U/mg, compared to all the tested media. On the other hand, for chitinase of M. anisopliae strain IBCB 425, the activity value was close to 0.60 U/mg. In contrast, for B. bassiana isolate ESALQ PL63, SDY medium was the best inducer for chitinase production, with a value of 0.90 U/mg. Regarding the nematicidal activity of the crude extracts, the reduction percentages were 58% for ESALQ PL63 and 100% for IBCB 425 in the case of animal parasites. For plant parasites, the reduction percentages were 19% for ESALQ PL63 and 71% for IBCB 425. Thus, the use of enzyme-rich crude extracts presents promising control options for pest control.

Milky latex produced by few and not all the plants are the treasure chest of various bioactive compounds with defensive potential against herbivores, insects and pathogens. Mankind have utilized latices in the preparation of novel plant-based therapies for centuries. Therefore, an attempt has been made to synthesis silver nanoparticles (AgNPs) using AgNO₃ as a precursor and latex from C. procera as a reducing agent. The surface plasmon absorption peak at 430 nm confirmed AgNPs formation. The sharp peak with narrow width illustrated the homogenous nature. The face centre cubic structure of AgNPs was confirmed by the XRD pattern. FT-IR analysis deduced that the bio-molecules in the latex of C. procera are responsible for the reduction of AgNO₃ to AgNPs. Biosynthesised L-AgNPs possessed well pronounced antibacterial activity against P. aeruginosa and K. pneumoniae. Anti-inflammatory activity of the nanoparticle determined by membrane stabilization and proteinase inhibitory assay was found to be in dose-dependent. LC₅₀ value of L-AgNPs was found to be 63.09 µg/mL against IV instar larvae of A. aegypti. Distinct morphological changes were observed in the mosquito larva on exposure to various concentrations of L-AgNPs.

Plants are sources of natural products that reflect the ecological interactions that shaped their secondary metabolism. Among those, phytochemicals with insect repellent activity have shown potential to be part of integrated pest management programs. In this study, we performed an initial screening of the repellent activities of five commercially available essential oils, as well as the essential oil of lemon catnip (Nepeta cataria var. citriodora Dumoulin ex Lej.) and related natural products against the common bed bug (Cimex lectularius L.). Additionally, we studied the effects of two different growing locations (Upper Deerfield and Pittstown, state of New Jersey, United States) on the chemical composition of three lemon catnip lines (commercial lemon catnips Richters and Jelitto, and lemon-scented catnip line CN5). The chemical composition of the essential oils was determined by gas chromatography-mass spectrometry (GC-MS) and the repellent activity was assessed by the petri dish method. Cinnamon bark, clove buds, citronella and geranium essential oils were as effective as N,N-diethyl-meta-toluamide (DEET), the gold standard of insect repellents, against bed bugs after one hour of exposure in vitro. The essential oil of lemon catnip and its major compounds citronellol and geraniol were also as repellent as DEET using the same test. Citral shows promising short-term repellency but is inferior to geraniol and citronellol for extended duration of repellency. As for the chemical variability of lemon catnip lines in different growing locations, CN5 line was not significantly affected by the different locations, while both commercial lines Richters and Jelitto had significantly higher proportions of geraniol when grown in Upper Deerfield. Richters lemon catnip produced more nepetalactone in its essential oil when cultivated in Pittstown. This study is the first report of the activity of lemon catnip essential oil as an insect repellent and emphasized the importance of ecological conditions for the production of natural products for pest control applications.

Rhizosphere bacterial infections are studied with great interest as it enlightens the idea of host-pathogen interaction combined with host defence adaptations. In this study, we are studying the ability of Hedychium forrestti var. forrestii rhizome against rhizosphere bacterial colonialization. It is understood that bacterial colonialization is immensely supported by biofilm production. We analyzed the biofilm inhibition efficacy of the plant rhizome extract, which suggested that the presence of plant rhizome extract could successfully downregulate the rate of bacterial adherence. The Spectrophotometrical data indicated that about 80% of biofilm production by Staphylococcus aureus can be inhibited by administering 500 µg/ml plant rhizome extract. The microscopic studies pointed out that antagonist-disabled bacteria form a film upon a given surface compared to untreated conditions. Fluorescence microscopy also identified that biofilm inhibition made bacteria more vulnerable. It was observed that the biofilm inhibition by plant rhizome extract is complimented by the amylolytic property of plant rhizome extract, verified by the enzyme kinetics studies. The plant rhizome extract process suggested a notable amylolytic action by Michaelis–Menten kinetics.

Termite, a havoc for infrastructure and agriculture, is still progressing its realm and continue its devastating activity to human habitat. Conventional chemicals are not sufficient to prevent infestation and are hazardous too for environment. Lantana camara, an imported wild weed, was analysed to assess the termiticidal potential. Present study was carried out after survey of termite infestation in plants which indicated that L. camara was least affected by termites in studied area thus selected to check anti-termite property against one of the pests Odontotermes obesus (Rambur). An invasive O. obesus brought from crop fields and reared in laboratory by maintaining termite mould like environment in specialized termite box in which temperature was sustained at 27 ± 5 ºC and humidity at 70 ± 5%. No choice test assay proved L. camara methanolic leaf extract was most lethal as responsible to induce 100% mortality and phytochemically most diverse among others. Among isolated phytoconstituents, terpenoids showed 100% mortality at 250 µg concentration. Terpenoids further resolved to find active constituents in which mortality obtained between 5% and 51%. LC4 content was most lethal and induced 51.66% mortality while two other contents LC5 and LC6 showed 30% mortality. GC-HRMS analysis showed that the LC-4 contained Phenol 2,4 di-tert butyl while LC5 contained Phenol 3,5 di-tert butyl and LC6 contained isoaromadendrene epoxide as active phytoconstituents. The results indicated that the detected compounds can be useful termiticidal phytochemicals and might be applicable as bioinsecticide.